ICD-10 Code E21.1 – Secondary Hyperparathyroidism, Not Elsewhere Classified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code E21.1 – Secondary hyperparathyroidism, not elsewhere classified
What it is
E21.1 identifies secondary hyperparathyroidism, a condition where the parathyroid glands become overactive because of another underlying disorder. Use this code when the record documents secondary, not primary, hyperparathyroidism.
Clinical signs
Clinical features vary; refer to documentation. Commonly, the chart may note parathyroid hormone excess related to chronic kidney disease, vitamin D deficiency, or another cause of calcium-phosphate imbalance.
When to use this code
Use E21.1 when the provider specifically documents secondary hyperparathyroidism and does not identify a more specific cause or classification. It may appear in nephrology, endocrine, or metabolic bone disorder records. If the note links the condition to an underlying disease, code that condition as directed by the record.
Do not use for
Do not use this code for primary hyperparathyroidism or unspecified hyperparathyroidism. Check documentation if the record only states elevated parathyroid hormone without confirming secondary hyperparathyroidism.
Coding tip
Confirm that “secondary” is documented explicitly and code the associated underlying condition when supported by the chart.